Johari-Goldstein relaxation as the origin of the excess wing observed in metallic glasses

Measurements of the shear loss modulus G of amorphous Zr65Al7.5Cu27.5 at 5.4 kHz were reported by Rosner, Samwer and Lunken-heimer. They observed that the measured G are in excess of the contribution from the alpha-relaxation, indicating the existence of an 'excess wing' in amorphous metals like that found in molecular glass-formers. They speculated that the excess wing found in amorphous metal is due to the presence of an unresolved Johari-Goldstein (JG) secondary relaxation. In this work, the coupling model is used to calculate the temperature T-JG, at which the JG relaxation frequency coincides with the experimental frequency of the isochronal measurement. The location of T-JG is well within the temperature range where the excess wing of Zr65Al7.5Cu27.5 appears at 5.4 kHz. Hence, the result supports the assertion of Rosner et al. that the excess wing found in the metallic glass originates from the intrinsic JG relaxation. (c) 2006 Elsevier B.V. All rights reserved.